Patent Literature 1 discloses a deformed folded dipole antenna including a first element forming a dipole antenna made of a conductor formed of a line and a second element disposed opposite to the first element across an insulator, which is made of a conductor formed of a line. In the deformed folded dipole antenna, a tip of the first element and a tip of the second element are connected to each other, and the first element and the second element are further bent. As a small antenna obtained by further downsizing the deformed folded dipole antenna, a small antenna disclosed in Patent Literature 2 has been known. In the small antenna, a part of a linear portion of an element of the deformed folded dipole antenna is configured to have an inductance shape (a crank shape or a shape whose shape width decreases toward a tip of the shape, for example, a triangular shape or a semielliptical shape).
On the other hand, as an antenna improved in a return loss of the deformed folded dipole antenna, a configuration disclosed in Patent Literature 3 has been known. In this configuration, a line width of the element of the deformed folded dipole antenna is adjusted so as to adjust an impedance and improve the return loss.
A deformed folded dipole antenna with an improved return loss (refer to Patent Literature 3) suffers from a problem that downsizing is difficult. On the other hand, there is a problem that makes it difficult to improve the return loss satisfactorily even if the configuration of Patent Literature 3 is applied to the downsized dipole antenna with a part of the linear portion formed in an inductance shape (refer to Patent Literature 2).